Among his important translations were those of Jewish philosopher ibn Gabirol's Fons Vitæ (Meqor Hahayim), which was mistakenly thought for several centuries to be the work of a Christian scholastic named Avicebron or Avecebrol. Gundissalinus also translated works of the major Muslim philosophers Avicenna and al-Ghazâlî.

Unlike most other translators, Gundissalinus also wrote independent philosophical works, that are believed to date from the second half of the 12th century, probably during the era of Archbishop John (1151–1166). His most well-known work is De Divisione Philosophiae (Of Divisions of Philosophy), in which he argued for a development of the traditional Quadrivium. He also wrote about theological topics like the creation of the world and the immortality of the soul. In addition to Gundissalinus' translation of Meqor Hahayim, the Aristotelian ideas of ibn Gabirol were also communicated to the Latin West through Gundissalinus' own writings On the Soul, On the Immortality of the Soul, On Unity, and The Procession of the World.